The present invention relates to power tools and, more particularly, to a gear assembly for a power tool.
A power tool, such as an electric impact wrench, includes a tool housing, a motor supported by the tool housing and connectable to a power source, the motor including a rotatable drive shaft having a gear, a gear assembly driven by the motor, and a drive assembly driven by the gear assembly and drivingly connected to a tool element to work on a workpiece.
In a typical power tool, a separate bearing assembly is provided at the interface between the gear assembly and the drive assembly to support the driven end of the drive assembly. The separate bearing assembly generally includes a bearing support supported by the tool housing and a bearing supporting the driven end of the drive assembly. The driven end of the drive assembly extends through the bearing assembly, to the motor side of the bearing assembly, and is drivingly engaged by the gear assembly on the motor side of the bearing assembly.
One problem with the above-described power tool is that the separate bearing assembly requires additional space in and adds length to the power tool.
Another independent problem with the above-described power tool is that the bearing assembly provides a somewhat rigid and unforgiving support of the driven end of the drive assembly.
A further independent problem with the above-described power tool is that the drive assembly typically includes some axial play. Excessive axial play results in inefficiency of the drive assembly and wear on the components of the drive assembly.
The present invention provides a gear assembly for a power tool which substantially alleviates the problems with the above-described power tools. The present invention provides a gear assembly in which components of the gear assembly, such as, for example, the ring gear and the planetary gear carrier member, provide the races for the bearing assembly.
More particularly, the present invention provides a gear assembly for a power tool, the power tool including a tool housing, a motor supported by the tool housing and connectable to a power source, the motor including a rotatable drive shaft having a gear end, the motor being operable to drive a tool element driven for working on a workpiece. The gear assembly is defined as including a gear assembly housing supported by the tool housing, a ring gear supported by the gear assembly housing, a planetary gear carrier member supported for rotation relative to the ring gear and defining a bearing race, a component of the gear assembly providing another bearing race, the carrier member being drivingly engageable with the tool element to drive the tool element, a plurality of planet gears supported by the carrier member and drivingly connectable to the gear end of the drive shaft, the plurality of planet gears interacting with the ring gear to rotatably drive the carrier member, and a plurality of bearing members supported between the first bearing race and the second bearing race.
Preferably, the ring gear has an end defining the first bearing race. The gear assembly may further include an annular retainer engaging each of the plurality of bearing members. Also, the gear assembly may further include a second planetary gear carrier member supported for rotation, and a plurality of second planet gears supported by the second carrier member, the plurality of second planet gears being rotatably driven by the gear end of the drive shaft and interacting with the ring gear to rotatably drive the second carrier member. In addition, the gear assembly may further include a carrier gear supported by the second carrier member for rotation with the second carrier member, the carrier gear engaging the first-mentioned plurality of planet gears to rotatably drive the first-mentioned carrier member. Preferably, the gear assembly is a two-stage planetary gear assembly.
Also, the present invention provides a power tool including a tool housing, a motor supported by the tool housing and connectable to a power source, the motor including a rotatable drive shaft having a gear end, the motor being operable to drive a tool element for working on a workpiece, and a gear assembly. The gear assembly is defined as including a gear assembly housing supported by the tool housing, a ring gear supported by the gear assembly housing, a planetary gear carrier member supported for rotation relative to the ring gear and defining a bearing race, another component of the gear assembly providing another bearing race, the carrier member being drivingly engageable with the tool element to drive the tool element, a plurality of planet gears supported by the carrier member and drivingly connectable to the gear end of the drive shaft, the plurality of planet gears interacting with the ring gear to rotatably drive the carrier member, and a plurality of bearing members supported between the first bearing race and the second bearing race.
Preferably, the ring gear has an end defining the first bearing race. The gear assembly may further include an annular retainer engaging each of the plurality of bearing members. Also, the gear assembly may further include a second planetary gear carrier member supported for rotation, and a plurality of second planet gears supported by the second carrier member, the plurality of second planet gears being rotatably driven by the gear end of the drive shaft and interacting with the ring gear to rotatably drive the second carrier member. In addition, the gear assembly may further include a carrier gear supported by the second carrier member for rotation with the second carrier member, the carrier gear engaging the first-mentioned plurality of planet gears to rotatably drive the first-mentioned carrier member. Preferably, the gear assembly is a two-stage planetary gear assembly.
Preferably, the power tool is an impact wrench. The power tool may further include a drive assembly drivingly connectable between the gear assembly and the tool element, the drive assembly including a ram member drivingly connected to the carrier member and including a ram lug, and an anvil member rotatably supported by the tool housing and including an anvil lug engageable with the ram lug to drive the anvil member, the anvil member being drivingly connectable to the tool element to rotatably drive the tool element.
In addition, the present invention provides an impact wrench including a tool housing, a motor supported by the tool housing and connectable to a power source, the motor including a rotatable drive shaft having a gear end, the motor being operable to drive a tool element for working on a workpiece, and a gear assembly. The gear assembly is defined as including a gear assembly housing supported by the tool housing, a ring gear supported by the gear assembly housing, a planetary gear carrier member supported for rotation relative to the ring gear and defining a second bearing race, a component of the gear assembly providing another bearing race, the carrier member being drivingly engageable with the tool element to drive the tool element, a plurality of planet gears supported by the carrier member and drivingly connectable to the gear end of the drive shaft, the plurality of planet gears interacting with the ring gear to rotatably drive the carrier member, and a plurality of bearing members supported between the first bearing race and the second bearing race.
Preferably, the ring gear has an end defining the first bearing race. The gear assembly may further include an annular retainer engaging each of the plurality of bearing members. Also, the gear assembly may further include a second planetary gear carrier member supported for rotation, and a plurality of second planet gears supported by the second carrier member, the plurality of second planet gears being rotatably driven by the gear end of the drive shaft and interacting with the ring gear to rotatably drive the second carrier member. In addition, the gear assembly may further include a carrier gear supported by the second carrier member for rotation with the second carrier member, the carrier gear engaging the first-mentioned plurality of planet gears to rotatably drive the first-mentioned carrier member. Preferably, the gear assembly is a two-stage planetary gear assembly.
The impact wrench may further include a drive assembly drivingly connectable between the gear assembly and the tool element, the drive assembly including a cam shaft connected to the carrier member for rotation with the carrier member, a ram member drivingly connected to the cam shaft and including a ram lug, and an anvil member including an anvil lug engageable with the ram lug to drive the anvil member, the anvil member being drivingly connectable to the tool element to rotatably drive the tool element. Also, the power source may be a battery, and the impact wrench may further include the battery supported by the tool housing. Preferably, the battery is removably supported by the tool housing.
One independent advantage of the present invention is that the gear assembly occupies a reduced space and provides a reduced length for the power tool.
Another independent advantage of the present invention is that the components of the drive assembly provide a less rigid and more forgiving (of radial misalignment) support of the drive assembly.
A further independent advantage of the present invention is that, in some aspects of the invention, the drive assembly includes a biasing member, such as, for example, an O-ring, which takes up unwanted axial play in the drive assembly and biases or pre-stresses the components of the drive assembly forwardly into engagement, improving the efficiency of and reducing the wear on the drive assembly.
Other independent features and independent advantages of the present invention will become apparent to those skilled in the art upon review of the following detailed description, claims and drawings.